1. Field of the Invention
This invention relates to a silicone water-based composition which is a storage stable, paste-type material that is useful as a caulking material.
2. Background Information
Silicone elastomeric emulsions having improved shelf life are taught by Elias and Freiberg in U.S. Pat. No. 4,427,811, issued Jan. 24, 1984. Their emulsion contains an anionically stabilized, hydroxyl endblocked polydiorganosiloxane, colloidal silica, and an alkyl tin salt. This mixture is aged for at least two weeks at room temperature, then filler other than colloidal silica is added. The emulsion can be used as a coating, or sufficient filler can be added to obtain a paste-type viscosity material useful as a caulking material. Experience has now shown that even using the method of their invention gives a product which slowly changes upon shelf aging. Particularly in regard to compositions useful as caulking materials, the slow change in properties of the emulsion causes a drop in the elongation of the cured elastomer produced by removing the water from the emulsion. A need was apparent for a composition useful as a caulking material which did not change in properties as rapidly as did the compositions of Elias and Freiberg.
Methods were known for producing silicone coating emulsions such as the cloth treating materials of Nelson, taught in Canadian Pat. No. 862,183, issued Jan. 26, 1971. His aqueous dispersion of liquid hydroxyl endblocked dimethylsiloxane polymer, a trifunctional or tetrafunctional alkylsilane, and siloxane condensation catalyst was useful in dilute emulsions as one-part or two-part compositions which were heated to cure the compositions. It is not feasible to heat compositions intended for use as caulking materials in most cases. Nelson teaches nothing concerning high solids content, filled compositions useful as caulking materials.
In U.S. Pat. No. 3,355,406, issued Nov. 28, 1967, Cekada teaches the use of silsesquioxane to reinforce silicone rubber latex. He teaches a latex containing a curable, essentially linear silicone polymer, preferably a hydroxy or alkoxy endblocked linear polymer having been prepared by emulsion polymerization, a cross-linking agent which is a trifunctional or tetrafunctional silane, preferably trialkoxysilane, and a catalyst. Included in the catalysts are dialkyltindiacylates. Cekada teaches nothing concerning compositions useful as caulking materials, nor does he indicate how shelf stable his emulsion may be.
An emulsion which is not storage stable is taught by Huebner in U.S. Pat. No. 3,706,695, issued Dec. 19, 1972, which describes a composition useful as an elastomeric electrically conductive coating. The method prepares a composition from an emulsified polydiorganosiloxane, carbon black, organometallic catalyst, and trifunctional silane.
A composition useful as a binder for making gaskets is taught by Ichikawa et al. in U.S. Pat. No. 4,100,124, issued July 11, 1978. Their composition, a mixture of hydroxyl endblocked polydiorganosiloxane, trialkoxysilane, organometallic catalyst, emulsifying agent, water and gasketing material is made into a sheet, compressed, dried, and thermally cured.
Huebner et al. teach a method of blending an aqueous emulsion of hydroxyl endblocked polydiorganosiloxane and an aqueous emulsion of copolymer of unsaturated organic monomer and unsaturated organosilicon monomer with an alkyl tin salt and a silane crosslinking agent in U.S. Pat. No. 4,288,356, issued Sept. 8, 1981. The product obtained by devolatilizing the blended emulsions is an elastomer useful as a coating, a textile treatment, and a paper treatment. They teach that if the copolymer emulsion is not present, the final product is a soft, sticky, polydiorganosiloxane gum which is not useful as an elastomeric product.
Another composition which cures to an elastomer upon removal of water is disclosed in Japanese Publication 57-57063, published Dec. 2, 1982, laid open to public inspection Nov. 15, 1978. The composition, composed of hydroxyl terminated diorganosiloxane, silane containing at least 3 silicon-bonded hydrolyzable groups, curing catalyst such as metal salt of organic acids, emulsifier, and water, is stated to be storage stable as a one-part emulsion which rapidly converts to an elastomer upon drying. The composition is useful as a coating agent or fiber processing agent. There is no suggestion that the composition is useful with fillers.
Experience shows a need for a composition useful as a caulking material that has improved shelf life. The above prior art shows conflicting results when an emulsion is prepared from hydroxyl endblocked polydiorganosiloxane, trifunctional or tetrafunctional alkylsilane, and siloxane condensation catalyst. Nelson teaches heat cure as does Ichikawa et al., while Huebner et al. and Japanese 57-57063 teach cure at room temperature. Huebner et al. '356 teach a soft, sticky gum is obtained without their copolymer, while Japanese 57-57063 shows an elastomer was obtained. Japanese 57-57063 also teaches that less than 50 parts by weight of water per 100 parts by weight of polymer is not recommended. None of the above references shows compositions useful as caulking materials which are based upon the use of hydroxyl endblocked polydiorganosiloxane, alkyl trialkoxysilane, dialkyltindicarboxylate, and non-siliceous filler.